A capacitance type physical quantity sensor apparatus is manufactured by stacking both a circuit chip and a sensor chip for detecting a physical quantity based upon a capacitance change between a movable electrode and a fixed electrode, while the physical quantity, for instance, an acceleration sensor, an angular velocity sensor, and the like, is applied to the capacitance type physical quantity sensor apparatus.
The sensor chip has been manufactured in such a manner that a movable electrode and a fixed electrode have been formed on a semiconductor layer. The semiconductor layer has been provided via an insulating layer on one plane side of a supporting substrate. The movable electrode can be displaced along a direction parallel to the plane of the supporting substrate in response to an applied physical quantity.
Then, in this sensor chip, when such a physical quantity as acceleration is applied thereto along a direction parallel to the substrate plane, a distance between the movable electrode and the fixed electrode is changed in response to this application of the physical quantity, and thus, the physical quantity is detected based upon a capacitance change defined between the movable electrode and the fixed electrode, which is caused by the above-explained distance change.
In this case, the sensor chip has been manufactured by employing such a stacked layer substrate that the semiconductor layer has been stacked via the insulating layer on the supporting substrate such as an SOI (silicon-on insulator) substrate, or the like.
For instance, a photo-etching process step is carried out from the front surface of the semiconductor layer so as to form trenches. These formed trenches are used to define patterns of both the movable electrode and the fixed electrode. Thereafter, an etching process is carried out from the supporting substrate so as to form an opening portion which is reached to the insulating layer.
Subsequently, the insulating layer which is contacted to the movable electrode is etched so as to be removed, so that the movable electrode is brought into a release condition. Thus, the sensor chip can be manufactured in accordance with this manner.
Then, this sensor chip has been stacked on a circuit chip on the side of the supporting substrate, and both the sensor chip and the circuit chip have been fixed to each other via an adhesive film, and the like. Also, the sensor chip has been electrically connected to the circuit chip by way of a bonding wire.
On the other hand, as to sensor chips having movable electrodes, such capacitance type acceleration sensors having structures in which glass caps for restricting excessively large displacement of the movable electrodes are covered on the sensor chips have been conventionally proposed, for example, in Japanese Laid-open Patent Application No. 2002-151703.
However, in such a conventional capacitance type physical quantity sensor apparatus, when an excessively large shock is applied along a thickness direction of the sensor chip, namely, along a stacked layer direction of both the sensor chip and the circuit chip, there are some possibilities that the movable electrode exceeds the range of the thickness thereof to be displaced along the above-explained direction, and then, this movable electrode runs onto the adjoining fixed electrode.
In particular, normally, a thickness of the supporting substrate which constitutes the sensor chip is considerably thicker than a thickness of the movable electrode, namely, a thickness of the semiconductor layer.
Then, in the sensor chip, since the opening portion has been formed in the supporting substrate which is located under the movable electrode, the movable electrode may be easily and largely displayed along the upper direction and the lower direction, namely the thickness direction of the sensor chip, and thus, as previously explained, the movable electrode may easily run onto the fixed electrode.
One conceivable idea for solving this technical difficulty, is to include a cap for covering a sensor chip and restricting large displacement of a movable electrode (mass body). In this conceivable idea, there are such problems that the cap member is required to separate, and since this cap is formed, the structure of the sensor apparatus becomes complex and the cumbersome manufacturing process is required.